Electron beam discharge device



April 21, 1942. A. mv GLOVER 2,280,228

ELECTRON BEAM DISCHARGE DEVICE Filed Jan. 51,1941

Patented Apr. 21, 1942 t UNlTE D- TSTATE S Pare r org es ELECTRON BEAM DISCHARGE DEVICE AlanlMg Glover. East Orange, N. J.,' assignor to Radio Corporation of America, a corporation of Delaware Application January 31, 1941, Serial No. 376,737 7 ecmims.

My invention relates to electron discharge de-.

vices, particularly to devices of the electronbeam forming type. l 1

Attempts have beenmadeto obtain high gain and high transconductance by mounting. a cath- 1 ode with beam forming electrodes on one side an annular space definedby two concentric cylinders and by so relating the potentials ,of the .The characteristicfeatures of my invention are defined in the appended claims andwcne embodiment thereof is described in the following specification and shown in the accompanying drawing inwhich Figure 1 is a longitudinal sectional view of an electron'discharge device embodying my invention; Figure 2 is a transverse sectional view of the tube shown in Figure 1 on line 2-2, and Figure 3 is one diagrammatic showing of circuit connections of the tube of Figures 1 and 2. l

The envelope l' of the electron discharge device as shown in Figure lis of metal, such as iron, and of the type usually used in the manufacture of conventional metal radio receiving tubes. The electrodes within the envelope are completely enclosed in metal except fora small glass header 2 of the button type sealed in one end of the envelope and carrying the lead-in conductors for the electrodes. Insulating spacer discs 3 of the conventional mica type support the electrodes at their ends. Centrally in the envelope is metal cylinder 4, and flattened indirectly heated cathode 5, mounted between the spacers, is parallel to the axis of the envelope and cylinder. Surrounding the cathode is control grid 6 of the wire-wound orladder type on two side rods.

Diametrically opposite the. cathode are mounted The control grid side rods are placed in a plane through the center of the tube.

(Cl. 250-275) H r the output electrodes 8. and 9 of the tube. "With the cathode at emission temperatur the potential of the accelerating electrodes 1 andcylinder 4, may be adjusted to direct two electron beams in opposite directions from the fiatsides of the cathode in circular paths and focused upon the output electrodes. comprise a first. and a second anode .side-by-side so that the beams may be deflected from one to the other by modulating the' potential of the inner cylinder 4. Alternatively, one anode may be coated with electron emitting material, such as metal oxides which will emit secondary electrons when bombarded by the primary electrons of the beams. The first anode 8, for example, may be coated with barium oxide on its surface opposite the second anode 9, When the first anode is struck by primary electrons a. larger number of secondary electrons areemitted and pass to the second anode 9. The tube thus constructed has an increased amplification factor and transconductance, and one circuit for this tube, more fully hereinafter described, is shown in Figure 3.

The electron beams originating at the cathode 7 appear to be deflected into cylindrical paths by the concentric metal cylinders 4 and envelope I, and if the potential of the cylinder is high with respect to the envelope, the beams follow the concentric equipotential lines of force to the output electrodes. The diameter of the circular paths of the beams may be materially changed by slight changes in the field between the two concentric cylinders, and because of the high susceptibility of the beams to the cylinder potentials, beam tubes made by the usual construc tion are undesirably afiected by external electromagnetic and electrostatic disturbances.

The beam tube constructed according to my invention is substantially free in operation of electrostatic as well as electromagnetic disturbances. The metal envelope of my tube is employed as one of the focusing electrodes for the beams, and it has been found that if the diameter of the metal envelope is sufficiently large, it

may be grounded and operated at Zero direct' current and high frequency potential. It has been found, further, that the cathode 6 should be placed nearer the inner cylinder 4 than the envelope, or inside a circle half way between the The output electrodes .may

of the envelope.

electromagnetic or electrostatic types exteriorly The elimination of one focusing electrode materially simplifies the manufacture of the tube. With the beams closer to the inner cylinder 4 than to the envelope wall, cylinder potential control over the beams is relatively greater than the control of the outer cylinder or envelope over the beams.

When the face of the first anode 8 is coated with electron emissive material, the tube may be connected as shown in Figure 3, an input circuit is connected between the control grid 6 and the cathode 5. The output circuit, including any suitable coupling device such as winding I0, is connected to the anode. The outer cylinder or envelope I is grounded and the inner cylinder 4 is connected to a high positive potential. The transconductance of the amplifier thus connected is the product of the control grid transconductance and the primary to secondary emission ratio of the collector 8. When the two anodes are placed side-by-side in the path of the beams and the beams shifted from one electrode to the other by modulating the potential on the inner cylinder 4, the output circuit would of course be connected between the two anodes. A second input circuit could then be connected to the cylinder 4, and the tube operated as a converter or mixer tube.

Good results have been obtained in mounting the electrodes of my novel tube in a metal envelope .930 inch in diameter, the inner cylinder having a diameter of .375 inch, with the cathode spaced about one-thirdthe distance from the inner cylinder toward the envelope, or about .565 inch between the cathode axis and envelope axis, and with the voltage on the inner cylinder being 200 volts, the accelerating electrode voltage being 200 volts, the first anode 8 voltage being 200 volts, the second anode voltage being 250 volts, and the control grid being 1.5 volts. With these dimensions and potentials the electron beam may be focused upon the center of the first anode 8 with the metal envelope grounded, giving an output current in the second anode circuit that did not change in the presence of strong electrostatic or electromagnetic fields about the tube.

I claim:

1. An electron discharge device comprising a cylindrical metal envelope adapted to be electrically grounded, a header closing one end of said envelope, lead-in conductors sealed in said header, a metal cylinder, smaller than said envelope, in and extending longitudinally of said envelope, a cathode in the annular space between the envelope and cylinder, a control grid around said cathode, and an output electrode in said annular space on the side of the cylinder opposite said cathode.

2. An electron discharge device comprising a cylindrical metal envelope, an elongated cathode, an elongated anode, said cathode and anode being spaced, parallel and disposed longitudinally of said envelope, a control grid surrounding said cathode, a cylindrical metal focusing electrode parallel to the axis of said envelope between said cathode and anode, and lead-in conductors sealed in said envelope and connected to said cathode, anode and focusing electrode, the electrodes within said metal envelope being so constructed and arranged that electron current may fiow between the anode and cathode with said envelope at ground potential.

3. An electron discharge device comprising a cylindrical envelope of ferro-magnetic metal, lead-in conductors hermetically sealed in one end of said envelope, a metal cylinder smaller in diameter than said envelope in and extending longitudinally of said envelope, said cylinder being disposed substantially centrally of said envelope, a cathode extending longitudinally of the envelope parallel to said cylinder and positioned closer to said cylinder than to said envelope, 2. control grid around said cathode, and an accelerating electrode adjacent said control grid, and an anode in said annular space diametrically opposite said cathode.

ALAN M. GLOVER. 

